Environmental Control System for a Vehicle

ABSTRACT

An environmental control system for a vehicle, in particular for predicting internal misting of a vehicle windscreen, the system comprising a windscreen temperature sensor assembly  28 , an ambient humidity sensor assembly  32  and a second temperature sensor assembly  30  for sensing the temperature of the humidity sensor assembly  32 . The windscreen temperature sensor assembly  28  is mounted on an interior rearview mirror support bracket  10  for engagement with the interior surface  18  of the windscreen, and the second temperature and humidity sensor assemblies are mounted within a rearview mirror housing  12  mounted to the mirror support bracket  10.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an environmental control system for a vehicle,and in a preferred aspect to a system for predicting internal misting(fogging) of a vehicle window, especially but not limited to a vehiclewindscreen.

2. Prior Art

U.S. Pat. No. 6,422,062 describes an integral sensor unit for predictingmisting of a vehicle windscreen. The unit comprises a windscreentemperature sensor assembly, an ambient second temperature sensorassembly and an ambient air humidity sensor assembly, all containedwithin a common dome-shaped housing. In use the housing is attached tothe interior surface of the windscreen and is connected via amulti-conductor lead to a control unit located away from the housing,e.g. in the vehicle header.

A disadvantage of this unit is that its presence on the windscreen canbe distracting to the driver and/or obscure his vision. Also, by placingthe ambient air temperature and ambient humidity sensor assemblies inthe same housing as the windscreen temperature sensor assembly they arenecessarily enclosed near to the windscreen and hence may not be trulyrepresentative of the ambient temperature or atmosphere in the mainpassenger cabin of the vehicle. The presence of the unit and its cablingmay also be aesthetically unattractive.

It is an object of the invention to provide an environmental controlsystem for a vehicle, and especially but not limited to an improvedsystem for predicting internal misting of a vehicle windscreen or otherwindow which avoids or mitigates these disadvantages.

SUMMARY OF THE INVENTION

According to one aspect of the present invention there is provided avehicle environmental control system comprising a window temperaturesensor assembly for sensing the temperature of an interior surface of avehicle window, a humidity sensor assembly for sensing the ambient airhumidity within the vehicle, and a second temperature sensor assemblyfor sensing the temperature of the humidity sensor assembly, wherein thesecond temperature and humidity sensor assemblies are mounted within thevehicle away from the window temperature sensor assembly.

An advantage of the invention is that it provides design freedom toplace the various sensor assemblies at positions most advantageous for agiven situation, where the driver would not normally be aware of theirpresence. Hence they are not likely to distract the driver or obscurehis vision. Further, by placing the second temperature and ambienthumidity sensor assemblies away from the window temperature sensorassembly, which must necessarily be on or very close to the window, theyare more likely to be representative of the ambient temperature oratmosphere in the main passenger cabin of the vehicle. Although in oneapplication the outputs of the sensor assemblies are used in combinationto predict internal window misting, their outputs can be usedindependently of each other, if desired, in order to measure thetemperature and/or the humidity of the cabin, for the purposes ofaltering the environmental conditions of the cabin itself, in particularfor the purposes of passenger comfort.

Preferably the window temperature sensor assembly is mounted forresilient biasing against the interior surface of the window.

In a preferred embodiment of the invention the system comprises awindscreen temperature sensor assembly for sensing the temperature ofthe interior surface of the windscreen, a humidity sensor assembly forsensing the ambient air humidity within the vehicle, and a secondtemperature sensor assembly for sensing the temperature of the humiditysensor assembly, wherein the windscreen temperature sensor assembly ismounted on an interior rearview mirror support bracket for engagementwith the interior surface of the windscreen, and wherein the secondtemperature and humidity sensor assemblies are mounted within a rearviewmirror housing mounted to the mirror support bracket.

In another aspect of the invention there is provided a temperaturesensor assembly comprising a thermally insulating body, a temperaturesensing element thermally insulated within the body, and a thermallyconductive contacting element exposed externally of the body and inthermal communication with the temperature sensing element.

In yet another aspect of the invention there is provided a temperaturesensor assembly comprising a thermally conductive element having asubstantially planar exposed upper surface, a temperature sensingelement in thermal communication with a lower surface of the thermallyconductive element, a plurality of leads for the temperature sensingelement extending downwardly away from said lower surface, and agenerally tubular thermally insulating housing assembly having an upperend surrounding and supporting the temperature sensing element, thetubular housing assembly extending downwardly away from said lowersurface of the thermally conductive element and having an internal airgap surrounding said leads.

In a still further aspect of the invention there is provided a mirrormounting system comprising a mounting bracket adapted for releasableconnection to a vehicle window, and a sensor resiliently mounted to thebracket at a position such that, when the bracket is connected to thevehicle window, the sensor is urged against the window.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of various aspects of the invention will now be described,by way of example, with reference to the accompanying drawings, inwhich:

FIG. 1 is a side view of a vehicle interior rearview mirror assemblyforming part of a vehicle environmental control system according to oneaspect of the invention.

FIG. 2 is an enlarged cross-section of one embodiment of a windscreentemperature sensor assembly forming part of the vehicle environmentalcontrol system.

FIG. 3 is a top perspective view of a mirror support bracket assembly ofFIG. 1, omitting a mirror housing.

FIG. 4 is a view of the interior of part of the mirror housing of FIG.1, omitting the reflective element.

FIG. 5 is a cross-section on line X-X of FIG. 4.

FIG. 6 is an external view of the part of the mirror housing shown inFIG. 4.

FIG. 7 is a perspective view of a temperature sensor assembly accordingto one aspect of the present invention.

FIG. 8 is a cross-section of a temperature sensor assembly according toa further aspect of the invention.

FIG. 9 shows the typical temperature distribution of a vehiclewindscreen and preferred location of the temperature sensor.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Referring now to the drawings, there is illustrated a vehicleenvironmental control system which comprises a mirror assemblycomprising a mirror support bracket 10 and a rearview mirror housing 12.The bracket 10 has an upper end 14 for releasable attachment to awindscreen mounting member 16 which is adhesively secured to theinterior surface 18 of the vehicle windscreen 20. The mounting member 16may take the form of a windscreen button, rails, or any other suitableattachment element. The lower end of the bracket 10 is in the form of aball 22, FIG. 3, which engages a complementary socket (not shown) withinthe mirror housing 12 to allow universal rotational adjustment of themirror. The mirror housing 12 has a front opening 24 which is normallyclosed by a reflective element (also not shown) held in place by a bezel26. The reflective element may comprise an electro-optic cell so thatthe reflectivity of the mirror can be varied according to prevailingconditions. The bracket 10 and mirror housing 12 are moulded from arigid plastics material. The construction and operation of interiorrearview mirror assemblies as just described are well-known to thoseskilled in the art and no further details are deemed necessary.

The environmental control system, of which the mirror assembly forms apart, is capable of performing a number of environmental controlfunctions, in particular but not exclusively predicting internal mistingof a vehicle window, for example a windscreen. The environmental controlsystem comprises a windscreen temperature sensor assembly 28 for sensingthe temperature of the interior surface of the windscreen, a secondtemperature sensor assembly 30, FIG. 5, in particular for sensing thetemperature of a humidity sensor assembly 32, which humidity sensorassembly 32 is operable to sense the ambient air humidity within thevehicle. The windscreen temperature sensor assembly 28 is mounted on thebracket 10 for engagement with the interior surface of the windscreen,while both the second temperature sensor assembly 30 and humidity sensorassembly 32 are mounted on a printed circuit board (PCB) 34, FIGS. 4 and5, within the mirror housing 12. The second temperature sensor assembly30 is preferably mounted on, or is in direct contact with, the humiditysensor assembly 32, in order to be capable of sensing the temperaturethereof, the reason for which is set out hereinafter. The secondtemperature sensor assembly is illustrated, in FIG. 5, as being separatefrom the

The windscreen temperature sensor assembly 28 is a generally cylindricalbody axially slidable within a hollow cylindrical sensor housingassembly 36, the latter being fitted into a hollow cylindrical moulding38 integral with the upper end 14 of the bracket 10. A highly thermallyconductive windscreen contacting element 42 is provided on the sensorassembly 28, which is preferably formed from a disc of metal or thelike, for example aluminium, copper, brass, etc. The contacting element42 is in thermal communication, preferably direct communication, with atemperature sensing element (not shown), preferably a thermistor,embedded within the temperature sensor assembly 28. A biasing means inthe form of a compression spring 40, acting between annular flanges onthe sensor assembly 28 and sensor housing assembly 36 respectively,resiliently biases the sensor assembly 28 at least partially out of thehousing 36 into contact with the interior surface 18 of the windscreen20.

An advantage of this arrangement is that a mounting system is provided,comprising the support bracket 10, which enables the sensor assembly 28to be urged into contact with the windscreen 20 simultaneous with theattachment/securing of the mounting bracket 10 to the mounting member 16on the windscreen 20. Thus no further operations are required in orderto correctly position the sensor assembly 28 against the windscreen 20,thereby rendering the mounting system extremely beneficial in assemblyline production of vehicles, allowing a “fit and forget” approach to beutilised. As the mirror assembly is attached to its windshield mountingbutton or other attachment member 16, the contacting element 42 of thesensor assembly 28 makes close and thermally intimate contact with theinner surface of the vehicle windshield.

The resilient mounting of the sensor assembly 28 performs two furtherimportant functions. The spring biasing of the sensor assembly 28ensures that the sensor assembly 28 makes intimate and thermallyconductive contact with the windscreen 20, in order to ensure that thesensor assembly 28, and in particular the contacting element 42, isthermally coupled with the windscreen 20, thus providing accuratereadings from the sensor assembly 28 of the actual surface temperatureat the inner surface of the vehicle windshield where dew/condensationmay form. It is desirable that this surface temperature be what ismeasured and not the temperature of the air in the cabin adjacent thewindshield (that may be at a higher temperature). In addition, theresilient mounting of the sensor assembly 28 allows for manufacturingtolerances, both in the mounting system itself and in the windscreen 20against which the mounting assembly is to be seated via connection tothe mounting member 16. It is well known that during the production of aproduct such as a vehicle or the like, having a large number ofinterrelated parts, manufacturing tolerances can accumulate, oftenresulting in a bad or inferior fit between various components. This canresult in time being wasted, slowing down production and increasing thecost thereof. The resilient mounting of the temperature sensor assembly28 allows for such variations in fit between the support bracket 10 andthe windscreen 20. The temperature sensor assembly 28, and in particularthe contacting element 42, prior to the mounting of the support bracket10, projects from the moulding 38 a distance greater than is necessaryto contact the windscreen 20. Thus when the support bracket 10 ismounted to the windscreen 20, the temperature sensor assembly 28 will bedisplaced inwardly against the action of the spring 40 in order toaccommodate this negative dimensional difference. This will then ensurethat the temperature sensor assembly 28 remains biased against thewindscreen during use, so achieving and maintaining intimate thermalcontact therewith.

From the foregone description it will be appreciated that the bracket 10may be used with a sensor assembly other than the temperature sensorassembly 28, for example a rain sensor assembly (not shown) or the like,which must be seated against a vehicle window for the correct operationthereof.

Referring now in particular to FIGS. 2 and 3, and as mentioned above,the temperature sensor assembly 28 preferably contains a temperaturesensing element in the form of a thermistor element connected to the PCB34 by a cable 44. In this embodiment the cable 44 passes from the sensorassembly 28 to the PCB 34 via a central bore 46 in the bracket 10, FIG.3. The bore 46 may also serve to allow electrical connection to otherelectronic equipment in the mirror housing 12, in a manner otherwiseknown to the automotive electrical connection art and thus will not befurther described.

The PCB 34 carrying the second temperature and humidity sensorassemblies 30, 32 is releasably mounted in the mirror housing 12 behindthe reflective element. It is held in place by resilient clips 48 (onlyone is shown in FIG. 4) with the surface of the PCB 34 which carries thesensor assemblies 30, 32 facing the rear of the housing 12. An internalwall 50, whose front edge 52 abuts against the rear surface of thereflective element when fitted to the open front 24, defines within themirror housing 12 a sub-compartment 54 containing the PCB 34. The PCB 34is thus substantially thermally isolated in the sub-compartment 54, thewall 50 comprising a thermal barrier to heat generated by otherelectronic devices, if any, in the main body of the mirror housing. Thecable 44 passes through a small hole (not shown) in the wall 50.Ventilation slots 56 in the rear of the housing, facing the surface ofthe PCB 34 carrying the second temperature and humidity sensorassemblies 30 and 32, allow ambient air to reach the sensor assemblies30, 32 within the sub-compartment 54. The number of ventilation slots 56is chosen such as to simulate, at least as closely as possible, theunobstructed flow of air past the second temperature and humidity sensorassemblies 30 and 32. In addition, as the natural flow of air within avehicle cabin, in the region of the mirror housing 12, is upwardly alongthe interior surface of the windscreen 20, the ventilation slots 56 arepreferably positioned on the rear of the mirror housing 12 to maximisethe flow of air therethrough and onto the temperature and humiditysensor assemblies 30 and 32. If desired, a fan may be provided foractively supplying air to the second temperature and humidity sensorassemblies 30, 32.

The PCB 34, and in particular the component-bearing side thereof facingthe ventilation slots 56, in addition to the second temperature sensorassembly 30 and humidity sensor assembly 32, are preferably colouredblack, so as to be rendered invisible through the ventilation slots 56,in order to improve the aesthetics of the mirror housing 12.

In addition to the sensor assemblies 30 and 32 the PCB 34 also bears acontroller (not shown) that includes a microprocessor that processes analgorithm including control logic which, in known manner, calculates theambient dew point from the ambient air temperature and humidity asmeasured by the sensor assemblies 30 and 32. However, it will beappreciated that said microprocessor may be located remotely of the PCB34, for example in separate control circuitry of the vehicle.

By mounting the second temperature sensor assembly 30 on or in directcontact with the humidity sensor assembly 32, the thermal mass of thehumidity sensor assembly 32 will not give rise to a lag between thereadings from the humidity sensor assembly 32 and the second temperaturesensor assembly 30, in particular during periods of temperature and/orhumidity fluctuation within the vehicle cabin. Thus it will beappreciated that the sensor assemblies 30, 32 could be located out ofcontact with one another, but the accuracy of any calculations based ontheir outputs may be negatively affected. If the sensor assemblies 30,32 are to be separate from one another, then said separation should bekept to an absolute minimum.

If the ambient dew point is greater than (or is calculated/predicted tobe imminently greater than) the temperature of the internal surface 18of the windscreen 20, the control unit provides a signal indicating thatthe windscreen is likely to mist up or is actually misted up. In eithercase the control unit can communicate via the bore 46 with a vehicleheating, ventilation and air conditioning system so that the latter iscontrolled to change the ambient conditions in the vehicle passengercompartment to reduce or avoid such misting up. As an alternative orcomplimentary function, the control unit may be adapted to deploy otherdemisting and/or environmental control strategies.

One of the advantages of the system of the present invention is that itfacilitates preemption of mist/fog build-up on the windshield surface sothat the HVAC system of the vehicle can be actuated to prevent anymisting occurring. This has an advantage over other known anti-foggingsystems such as those based on optical detection of mist/fog build-up(such as via an optical sensor or a camera sensor) as these othersystems typically operate to remove mist/fog as it is building up (orafter it has built up). By contrast, the present embodiment is operableto prevent mist/fog from occurring.

Although the foregoing has described an embodiment in which the sensorassembly 28 is mounted on the mirror support bracket 10 for sensing thetemperature of the interior surface of the windscreen 20, the sensorassembly 28 could alternatively by mounted in a suitable holder forsensing the temperature of the internal surface of any window of thevehicle, such as the rear window or a side window, in order to be ableto predict misting of such window. Furthermore, the second temperaturesensor assembly 30 and humidity sensor assembly 32 can be locatedelsewhere than in the mirror housing 12. For example, they could bemounted in the vehicle header 60, or in an electronics housing 62located on the inside of the windscreen 20 between the vehicle headerand the mirror support bracket 10. For example, the second temperaturesensor assembly 30 and/or the humidity sensor assembly 32 can beincluded in a windshield electronics module such as are described inU.S. Pat. Nos. 6,824,281 and 6,690,268.

The outputs of the sensor assemblies 28, 30 and 32 may be usedindependently of one another by the controller to control otherenvironmental aspects of the vehicle, such as internal humidity and airtemperature.

Referring now to FIG. 7, there is illustrated an enlarged view of thetemperature sensor assembly 28. The temperature sensor assembly 28comprises a highly thermally conductive windscreen contacting element 42which is preferably formed from a disc of metal such as aluminium,brass, copper, etc. The sensor assembly 28 further comprises atemperature sensing element in the form of a thermistor (not shown)embedded within a body 70 of highly thermally insulating material,preferably a polymeric material. The thermistor is in thermal contact,preferably direct contact, with the underside of the contacting element42. In this way the contacting element 42 acts as a thermal couplingbetween the windscreen 20 and the thermistor within the body 70 suchthat the thermistor principally senses only the temperature at thewindshield surface.

It will thus be appreciated that as the thermistor is embedded withinthe body 70, the contacting element 42 is the principal thermallyconductive portion of the sensor assembly 28 which is exposed, and whichin use will be urged against a vehicle window. It will therefore beappreciated that the temperature reading given by the temperature sensorassembly 28 will not be unduly affected by external factors such as thetemperature of the air located directly adjacent the vehicle window,which in the absence of the thermally insulating body 70 could alter thetemperature of the thermistor, and therefore the readings derivedtherefrom. The provision of the thermally insulating body 70 thereforeimproves the accuracy of the temperature sensor assembly 28. Although inuse the temperature sensor assembly 28 will be spring biased against avehicle window such as the windscreen 20, it is also envisaged that thecontacting element 42 could itself be spring biased within the body 70,in order to further ensure an intimate thermally conductive contactbetween the contacting element 42 and the windscreen 20.

The temperature sensor assembly 28 further comprises a cable 44 inelectrical connection with the thermistor, for electrically connectingthe temperature sensor assembly 28 to any suitable circuitry (notshown), for example the PCB 34. As the cable 44 contacts the thermistor,the possibility exists for the cable 44 to act as a thermal sink. Thiscould result in heat/cold being transferred to the thermistor, alteringthe temperature of the thermistor, and so distorting the readingsderived therefrom. Thus to further improve the accuracy of measurementof the inner surface temperature of the windshield by the temperaturesensor assembly 28, the cable 44 is preferably jacketed by thermallyinsulating material, or alternatively is formed from a conventionalelectrical conductor provided with a thermally insulating coating or thelike (not shown) but with care being taken to minimize thermal transferat the point that the electrical conductors within the cable makecontact with the thermistor. This ensures that heat transfer cannotoccur back along the cable 44.

FIG. 8 is a cross-section of a substantially circularly symmetrictemperature sensor assembly 100 according to a further embodiment of theinvention, which may be used in place of the sensor assembly 28previously described and which we have found to provide a more accuratemeasurement of temperature than the previous sensor. In the followingdescription of FIG. 8, and in the related claims, terms of orientationand direction such as “upper”, “lower”, “downwardly” and the like referto the orientation of the sensor assembly as seen in FIG. 8 and do notlimit its orientation in use.

The sensor assembly 100 comprises a generally tubular housing assembly102 comprising, in this embodiment, three parts—an upper part 104, alower part 106 and an intermediate part 108 interposed between the upperand lower parts. The upper and lower parts 104, 106 have thecross-sectional shapes shown and are moulded from a thermally insulatingplastics material, while the intermediate part 108 comprises a thermallyinsulating resiliently deformable material, in particular a foamannulus.

The bottom surface of a substantially flat circular copper plate 110 issupported by and is adhered to the top surface of the upper housing part104, the bottom surface of the plate 110 having at its centre anintegral tubular copper housing 112 which extends downwardlyconcentrically within the upper housing part 104. A temperature sensingelement in the form of a thermistor 114 is secured within the copperhousing 112 by a thermally conductive potting compound 116, thethermistor 114 being in intimate contact with the lower surface of thecopper plate 110.

Thermistor leads 118 extend downwardly through the lower housing part106, the latter having an internal air gap 120 surrounding the leads. Aplug 122 of thermally insulating material is preferably but notessentially provided, in order to close the lower end of the housingpart 106, the leads then passing through the plug 122. The upper ends ofthe leads 118, where they emerge from the thermistor 114, are protectedby a tubular shroud 124 which forms part of the thermistor as acommercially available product.

A thermally conductive polymer layer 126 covers the copper plate 110,the upper substantially flat surface of the plate 110 making intimatelarge-area contact with the lower surface of the layer 126. The uppersurface 128 of the layer 126 is substantially planar, but has sufficientflexibility or compliance to conform closely to the inside surface of awindscreen or other window against which the sensor assembly 100 isbiased. The provision of the resiliently deformable intermediate part108 also enables the various components supported thereby, in particularthe thermistor 114, the copper plate 110, and the polymer layer 126, tobe urged against a vehicle windscreen in similar fashion to the actionprovided by the spring 40 used with the windscreen temperature sensorassembly 28.

The polymer layer 126 extends onto the periphery of the upper housingpart 104, thereby covering a lateral air gap 130 between the outsideperiphery of the metal plate 110 and the upper housing part 104. A smallbleed hole 132 provides an escape path for air which might otherwisebecome trapped between the polymer layer 126 and plate 110 when theformer is applied to the latter during manufacture.

In use the sensor assembly 100 may be mounted on a mirror supportbracket, such as the bracket 10 (FIGS. 1 to 3), and in particular in amoulding similar to the moulding 38. The resiliently deformableintermediate part 108 therefore serves a dual purpose, both thermallyinsulating the thermistor 114 and ensuring that the polymer layer 126 isspring biased against the windscreen. Thus, as in the case of theembodiment of FIGS. 1 to 3, the sensor assembly 100, and in particularthe upper surface 128 of the polymer layer 126, is automatically urgedinto, and maintained in, intimate contact with the inside surface of thewindscreen when the bracket 10 is mounted on its windscreen mountingmember 16.

In order to further thermally insulate the thermister 114, contactbetween the tubular housing assembly 102 and the bracket 10, inparticular the moulding 38, is preferably kept to a minimum in order toreduce possible thermal leak between the bracket 10 and the sensorassembly 100. Thus, for example, a number of radially extending fins(not shown) or the like may be provided on the underside of the flange134, in order to reduce the physical contact area between the flange 134and the moulding 38, and thus reduce possible thermal leak therebetween.For stability, it is preferable to provide at least three such fins,spaced approximately 1200 from one another. While more than three finscould be employed, this would increase the overall contact area betweenthe flange 134 and the moulding 38. Similarly, a number oflongitudinally extending fins (not shown) are preferably provided on theexterior of the lower housing part 106, again to act as a thermal bufferbetween the sensor assembly 100 and the moulding 38, while securing thesensor assembly 100 centrally within the moulding 38. Again thepreferred number of longitudinally extending fins is three.

The advantage of this design is that the thermistor 114 is substantiallythermally isolated from the environment by the three-part tubularhousing assembly 102 and by the static air trapped in the air gaps 120and 130. Thus the output of the thermistor 114 will more accuratelyreflect the temperature of the windscreen, or other surface againstwhich the polymer layer 126 is pressed, due to the high conductivity ofthe copper plate 110 and thinness of the polymer layer 126. Further, theuse of the polymer layer 126 lends itself better to the problem ofsliding the sensor assembly 100 across the windscreen during themounting of the bracket 10. It will be noted that in use the exposedpart of the sensor assembly 100, being primarily the portion above theflange 134, is relatively short and broad, thereby avoiding unnecessarythermal exposure and reducing the possibility of inadvertent damageduring mounting which might occur with a tall sensor assembly.

It should also be appreciated that the polymer layer 126 could beapplied to the windscreen temperature sensor assembly 28 in order toimprove the performance thereof. The polymer layer 126 could be applieddirectly onto the contacting element 42, or could be provided as asubstitute for same.

Preferably the entire sensor assembly 100 has a low thermal mass, inorder to avoid unduly affecting the temperature reading as might occurif the assembly 100 absorbed substantial heat from the windscreen.

It will be appreciated that as the second temperature sensor assembly 30and the humidity sensor assembly 32, in particular the secondtemperature sensor assembly 30, are mounted away from the windscreen 20,they are capable of measuring the temperature and humidity respectivelyof the cabin of a vehicle, as opposed to the air located directlyadjacent the windscreen 20 thereof. Thus the outputs of the secondtemperature sensor assembly 30 and the humidity sensor assembly 32 maybe used other than in combination with the output of the temperaturesensor assembly 28 or 100, in order to measure and consequently vary thetemperature and/or humidity of the cabin, for reasons other than thepossibility of misting of the vehicle windscreen 20, in particular forpassenger comfort. The positioning of the sensor assemblies 30 and 32within the mirror housing 12 is thus beneficial, as the sensorassemblies 30 and 32 are thus located close to a drivers upper body andhead area, which are generally the most sensitive areas to environmentalconditions.

FIG. 9 shows the typical temperature distribution of a vehiclewindscreen. In FIG. 9 the lightest areas are the hottest, and it willtherefore be seen that the upper 30 windscreen area is furthest fromheat sources such as air-conditioning/heating outlets and this upperwindshield area is the position where mist on the windshield will belast located during the demisting process. The upper windshield areaalso corresponds to a driver's line of sight. Thus, the upper windshieldarea is the preferred location of the temperature sensor assembly 28 or100.

1. A vehicle environmental control system comprising a windowtemperature sensor assembly for sensing the temperature of an interiorsurface of a vehicle window, a humidity sensor assembly for sensing theambient air humidity within the vehicle, and a second temperature sensorassembly for sensing the temperature of the humidity sensor assembly,wherein the second temperature and humidity sensor assemblies aremounted within the vehicle away from the window temperature sensorassembly.
 2. A system as claimed in claim 1, wherein the vehicle windowis the windscreen.
 3. A system as claimed in claim 1, wherein the windowtemperature sensor assembly is mounted on an interior rearview mirrorsupport bracket.
 4. A system as claimed in claim 1, wherein the secondtemperature and humidity sensor assemblies are mounted adjacent an upperportion of the window.
 5. A system as claimed in claim 1, wherein thesecond temperature and humidity sensor assemblies are mounted within arearview mirror housing.
 6. A system as claimed in claim 5, wherein thesecond temperature and humidity sensor assemblies are mounted on acircuit board within the mirror housing, and the window temperaturesensor assembly is connected to the circuit board by a cable.
 7. Asystem as claimed in claim 6, wherein the cable passes through a bore ina mirror support bracket for the mirror housing.
 8. A system as claimedin claim 5, wherein the mirror housing has ventilation openings to allowambient air to reach the second temperature and humidity sensorassemblies within the mirror housing.
 9. A system as claimed in claim 8wherein the ventilation openings are located in the rear of the mirrorhousing.
 10. A system as claimed in claim 8, wherein the number ofventilation openings is sufficient to simulate the unobstructed flow ofair past the second temperature and humidity sensor assemblies.
 11. Asystem as claimed claim 8, wherein aspiration means are provided foractively supplying air to the second temperature and humidity sensorassemblies.
 12. A system as claimed in claim 11 wherein the aspirationmeans comprises a fan.
 13. A system as claimed in claim 5, wherein themirror housing has at least one internal wall defining a sub-compartmentwithin the mirror housing containing the second temperature and humiditysensor assemblies.
 14. A system as claimed in claim 1, wherein thesecond temperature and humidity sensor assemblies are mounted within avehicle header.
 15. A system as claimed in claim 1, wherein the secondtemperature and humidity sensor assemblies are mounted within anelectronics housing located between a vehicle header and an interiorrearview mirror support bracket.
 16. A system as claimed in claim 1,wherein the window temperature sensor assembly is maintained in directengagement with the interior surface of the window.
 17. A system asclaimed in claim 1, wherein the window temperature sensor assembly ismounted for resilient biasing against the interior surface of the thewindow.
 18. A system as claimed in claim 1, wherein the output of thesecond temperature sensor assembly may be used for environmental controlindependently of the other sensor assemblies.
 19. A system forpredicting internal misting of a vehicle windscreen, the systemcomprising a windscreen temperature sensor assembly for sensing thetemperature of the interior surface of the windscreen, a humidity sensorassembly for sensing the ambient air humidity within the vehicle, and asecond temperature sensor assembly for sensing the temperature of thehumidity sensor assembly, wherein the windscreen temperature sensorassembly is mounted on an interior rearview mirror support bracket forengagement with the interior surface of the windscreen, and wherein thesecond temperature and humidity sensor assemblies are mounted within arearview mirror housing mounted to the mirror support bracket.
 20. Atemperature sensor assembly comprising a thermally insulating body, atemperature sensing element thermally insulated within the body, and athermally conductive contacting element exposed externally of the bodyand in thermal communication with the temperature sensing element.
 21. Atemperature sensor assembly according to claim 20 wherein thetemperature sensing element comprises a thermistor.
 22. A temperaturesensor assembly according to claim 20, wherein the contacting element issubstantially planar.
 23. A temperature sensor assembly according toclaim 20, wherein the contacting element comprises a metal disc.
 24. Atemperature sensor assembly according to claim 20, wherein the body isformed from a polymer.
 25. A temperature sensor assembly according toclaim 20, wherein the contacting element is resiliently mounted to thebody.
 26. A temperature sensor assembly according to claim 20 furthercomprising a cable connected to the temperature sensing element, thecable being thermally insulated.
 27. A temperature sensor assemblycomprising a thermally conductive element having a substantially planarexposed upper surface, a temperature sensing element in thermalcommunication with a lower surface of the thermally conductive element,a plurality of leads for the temperature sensing element extendingdownwardly away from said lower surface, and a generally tubularthermally insulating housing assembly having an upper end surroundingand supporting the temperature sensing element, the tubular housingassembly extending downwardly away from said lower surface of thethermally conductive element and having an internal air gap surroundingsaid leads.
 28. A temperature sensor assembly according to claim 27,wherein the tubular housing assembly comprises an upper part surroundingand rigidly supporting the sensing element, a lower part surrounding theleads, and a resilient member interposed between the upper and lowerparts.
 29. A temperature sensor assembly according to claim 28, whereinthe resilient member comprises a thermally insulating resilient foam.30. A temperature sensor assembly according to claim 27, wherein thethermally conductive element comprises a layer of a compliant thermallyconductive polymer.
 31. A temperature sensor assembly according to claim30, further including a metal plate having an upper surface in contactwith the lower surface of the polymer layer and a lower surface incontact with the temperature sensing element, the metal plate andpolymer layer being supported by the upper end of the tubular housingassembly.
 32. A temperature sensor assembly according to claim 31,further including a lateral air gap between the outside periphery of themetal plate and the upper end of the tubular housing assembly, the gapbeing covered by the polymer layer.
 33. A temperature sensor assemblyaccording to claim 27, further including a plug closing the lower end ofthe tubular housing assembly, the leads passing through the plug.
 34. Amirror mounting system comprising a mounting bracket adapted forreleasable connection to a vehicle window, and a sensor assemblyresiliently mounted to the bracket at a position such that, when thebracket is connected to the vehicle window, the sensor assembly is urgedagainst the window.
 35. A mirror mounting system according to claim 34,further comprising a sensor housing for receiving the sensor assembly,and biasing means arranged to urge the sensor assembly partially out ofthe sensor housing for contact with the window.
 36. A mirror mountingsystem according to claim 35, wherein the biasing means comprises aspring disposed between the housing and the sensor assembly.